1. Field of the Invention
The present invention relates generally to telecommunications systems and methods for monitoring satellite resources, and specifically to optimization of calls based upon the amount of available satellite resources.
2. Background and Objects of the Present Invention
Cellular telecommunications is one of the fastest growing and most demanding telecommunications applications. Today it represents a large and continuously increasing percentage of all new telephone subscriptions around the world. A standardization group, European Telecommunications Standards Institute (ETSI), was established in 1982 to formulate the specifications for the Global System for Mobile Communication (GSM) digital mobile cellular radio system.
With reference now to FIG. 1 of the drawings, there is illustrated a GSM Public Land Mobile Network (PLMN), such as cellular network 10, which in turn is composed of a plurality of areas 12, each with a Mobile Services Center (MSC) 14 and an integrated Visitor Location Register (VLR) 16 therein. The MSC/VLR areas 12, in turn, include a plurality of Location Areas (LA) 18, which are defined as that part of a given MSC/VLR area 12 in which a mobile station (MS) 20 may move freely without having to send update location information to the MSC/VLR area 12 that controls the LA 18. Each Location Area 12 is divided into a number of cells 22. Mobile Station (MS) 20 is the physical equipment, e.g., a car phone or other portable phone, used by mobile subscribers to communicate with the cellular network 10, each other, and users outside the subscribed network, both wireline and wireless.
The MSC 14 is in communication with at least one Base Station Controller (BSC) 23, which, in turn, is in contact with at least one Base Transceiver Station (BTS) 24. The BTS is the physical equipment, illustrated for simplicity as a radio tower, that provides radio coverage to the geographical part of the cell 22 for which it is responsible. It should be understood that the BSC 23 may be connected to several base transceiver stations 24, and may be implemented as a stand-alone node or integrated with the MSC 14. In either event, the BSC 23 and BTS 24 components, as a whole, are generally referred to as a Base Station System (BSS) 25.
With further reference to FIG. 1, the PLMN Service Area or cellular network 10 includes a Home Location Register (HLR) 26, which is a database maintaining all subscriber information, e.g., user profiles, current location information, International Mobile Subscriber Identity (IMSI) numbers, and other administrative information. The HLR 26 may be co-located with a given MSC 14, integrated with the MSC 14, or alternatively can service multiple MSCs 14, the latter of which is illustrated in FIG. 1.
The VLR 16 is a database containing information about all of the Mobile Stations 20 currently located within the MSC/VLR area 12. If a MS 20 roams into a new MSC/VLR area 12, the VLR 16 connected to that MSC 14 will request data about that Mobile Station 20 from the HLR database 26 (simultaneously informing the HLR 26 about the current location of the MS 20). Accordingly, if the user of the MS 20 then wants to make a call, the local VLR 16 will have the requisite identification information without having to reinterrogate the HLR 26. In the aforedescribed manner, the VLR and HLR databases 16 and 26, respectively, contain various subscriber information associated with a given MS 20.
It should be understood that the aforementioned system 10, illustrated in FIG. 1, is a terrestrially-based system. In addition to the terrestrially-based systems, there are a number of satellite systems, which work together with the terrestrially-based systems to provide cellular telecommunications to a wider network of subscribers. This is due to the fact that the high altitude of the satellite makes the satellite visible (from a radio perspective) from a wider area on the earth. The higher the satellite, the larger the area that the satellite can communicate with.
Within a satellite-based network 205, as shown in FIG. 2 of the drawings, a system of geostationary satellites 200 in orbit (one of which is shown) are used to provide communication between Mobile Stations (MS) 20 and a satellite-adapted Base Station System (SBSS) 220, which is connected to an integrated Mobile Switching Center/Visitor Location Register (MSC/VLR) 240. The MS 20 communicates via one of the satellites 200 using a radio air interface, for instance, based on the Time Division Multiple Access (TDMA) or Code Division Multiple Access (CDMA). The satellite 200 in turn communicates with one or more SBSSs 220, which consist of equipment for communicating with the satellites 200 and through the satellites 200 to the Mobile Stations 20. The antennae and satellite tracking part of the system is the Radio Frequency Terminal (RFT) subsystem 230, which also provides for the connection of the communication path to the satellite 200.
In such satellite networks 205 using geostationary satellites 200, the coverage area for a satellite 200 can be (and usually is) very large. This area can be served by a number of MSC/VLRs 240 which are connected to Public Switched Telephone Networks (PSTNs) (wireline networks), PLMNs (cellular networks) and each other. The terrestrial interconnections (trunk circuits) to these MSC/VLRs 240 are expensive to install and maintain, especially in comparison to handling the traffic over the satellite 200. Currently, the terrestrial trunk circuits are leased or owned by the operator, and in some cases, may need to be installed when the satellite network 205 is commissioned. Since the distances within the area served by the satellite(s) 200 are typically very large, the costs for these circuits can be enormous. In particular, the costs can be considerable if the circuits must cross remote areas or oceans.
Thus, as shown in FIG. 3 of the drawings, calls can be optimized using satellite resources by moving a mobile subscribers registration from a serving MSC/VLR 240a to an optimum MSC/VLR 240b. This can be accomplished by sending the Called Party Number (CPN) using, for example, an Unstructured Supplementary Services Data (USSD) string, to a Call Optimization Server (COS) 250 via the serving SBSS 220a and the serving MSC/VLR 240a. The COS 250 performs a pre-analysis on the CPN to determine the optimum MSC/VLR 240b, e.g., the MSC/VLR 240b with either the closest connection to the called subscriber 260 or the MSC/VLR 240b with the least expensive link to the called subscriber 260. Thereafter, the address of the optimum MSC/VLR 240b is returned to the MS 200 which can then register with the indicated MSC/VLR 240b. Once the registration is complete, the MS 200 can send a SETUP message to the new MSC/VLR 240b via the new SBSS 220b, and the call can be completed.
However, optimizing the use of terrestrial circuits by using a different satellite access for radio connectivity can create overconsumption problems for some network operators. Typically, when a call is optimized from the serving MSC/VLR 240a belonging to a first network operator 270 to the optimal MSC/VLR 240b with satellite radio access capabilities, that optimal MSC/VLR 240b belongs to another network operator 275. The satellite resources are generally apportioned to different operators 270 and 275 and different MSC/VLR's 240, with reserve satellite capacity left in a central "pool." If optimization requires a number of subscribers assigned to the first network operator 270 to be reassigned to an MSC/VLR 240b served by a second network operator 275, the reassigned subscribers could consume an excessive amount of satellite resources on the second network operator's 275 system, such that the subscriber's "belonging" to the second network operator 275 would not be able to access the system.
In addition, roaming agreements between network operators 270 and 275 typically provide for a wholesale, flat rate or free charge for serving subscribers associated with the other network operator 270 or 275. These charges are typically less than the charges the network operator's 270 and 275 own subscribers would pay. Therefore, when overconsumption by another network operator's 270 or 275 subscribers occurs, the result for the network operator 270 or 275 providing donor radio access is a loss of revenue and degraded service for their own subscribers.
It is, therefore, an object of the present invention to optimize satellite resources to prevent overconsumption of satellite resources of a first network operator by subscribers associated with a second network operator.